Narrated `Amr: Jabir bin `Abdullah said, Mu`adh bin Jabal used to pray with the Prophet and then go to lead his people in prayer Once he led the `Isha' prayer and recited Surat Al-Baqara. Somebody left the prayer and Mu`adh criticized him. The news reached the Prophet and he said to Mu`adh, 'You are putting the people to trial,' and repeated it thrice (or said something similar) and ordered him to recite two medium Suras of Mufassal. (`Amr said that he had forgotten the names of those Suras).